Ink-jet devices fire droplets of ink toward a printing medium, such as paper or Mylar. Typical ink-jet printheads comprise at least one group of nozzles, called a primitive, through which the droplets of ink are fired. For full color printing, three primitives are employed, with the nozzles of each fluidically connected to a reservoir of a different color ink (cyan, yellow, magenta). The firing, or propelling of ink droplets, may be done by piezoelectric means or by resistive heating (thermal).
In green, red and blue solid area-fill, the colors are generated by placing one dot of a first color on top of another dot of a second color, which produces the desired third color (e.g., yellow on cyan creates green). In the normal printing mode, the dots are put down on each other in the same pass of the printhead across the medium.
In one prior art U.S. Pat. No. i.e., 4,320,406, a printer utilizes adjacent nozzles 80 of primary colors magenta (M), yellow (Y), and cyan (C), with the color primaries adjacent one another; cf. FIG. 3 herein. This arrangement does not allow the primaries to overlap, and the patent makes no claim as to the quality of its product. The inventor used the layout to reduce the number of heads being accelerated and decelerated and also to minimize the space required. Without overlap, a larger head is needed; if three colors are used, two extra swaths are required at the beginning and end of an image, and if four colors are used, three extra swaths are required at the beginning and end.
In another prior art U.S. Pat. No. i.e., 4,540,996, the print method employs nozzles grouped in primitives, or printheads 90A, B, C and D, but the nozzles within each primitive or printhead 93 are not adjacent, where "adjacent" means "placed at one dot intervals or row from each other". One dot row is the distance defined by the printer resolution. For example, a 300 dot per inch printer has dot rows that are 1/300 inch (0.00333 inch) apart. Adjacent nozzles, then are 1/300 inch, or one dot row apart. Thus, for an equal number of nozzles, the printhead must be larger in the prior art printer; cf. FIG. 4 herein.
The configuration presented by FIG. 3 of the patent (FIG. 4 herein) will produce different hues. The configuration of FIG. 6 in the patent requires five extra swaths, or scans, at the beginning and end of a color image. The configuration of FIG. 10 in the patent requires six extra swaths at the beginning and end of a color image. As a result, the patented system requires more time and a larger printhead than the present method with an equal number of nozzles.
When printing a block of area-fill, bands occur between swaths of print rows, a swath being what is printed during a pass of the printhead or printheads across the medium by multiple nozzles one dot apart. The bands are caused by absorption of the first color printed on the medium, which may be a specially coated paper used for color ink-jet printing. The banding tends to reduce the perceived quality of the output.
Accordingly, a method of producing a substantially uniform block of color, without the perceived banding or at least with reduced perceived banding is desired.